1. Technical Field
The present invention relates to an electro-optical apparatus and a manufacturing method thereof, and to an electronic apparatus that includes the electro-optical apparatus.
2. Related Art
An example of the captioned electro-optical apparatus is an actively driven liquid crystal device employed as an optical modulator of a liquid crystal projector. The liquid crystal device has a pixel region including pixel electrodes arranged in a matrix pattern, thin film transistors (hereinafter, TFT) that perform switching control of the pixel electrodes, and a retention capacitance for retaining image signals written in the pixel electrodes, and a peripheral region including a scanning line driver circuit and a data line driver circuit for actively driving the pixel region.
It is desirable that such a liquid crystal device display brighter images with higher contrast, and therefore it is necessary to minimize factors that shield light in the pixel region, and to increase the retention capacitance to thereby improve the potential retention characteristic of the pixel electrodes. Accordingly, for example JP-A-2007-3903 proposes forming a transparent retention capacitance by employing a light-transmissive electrode constituted of indium tin oxide (ITO), so that the opening region of the pixel electrode is not optically blocked despite increasing the size of the retention capacitance.
In the liquid crystal device according to JP-A-2007-3903, however, a global step is formed along the outer periphery of the region where the retention capacitance is provided (hereinafter referred to as retention capacitance region), which disturbs the alignment of the liquid crystal molecules thus making the display uneven. This aspect will be described in further details here below.
According to JP-A-2007-3903, an interlayer dielectric is formed so as to cover the transparent retention capacitance, and the transparent pixel electrode is formed on the interlayer dielectric after a chemical mechanical polishing (hereinafter, CMP) process is applied to the interlayer dielectric for planarization. In the thus-configured liquid crystal device, light is reflected at an interface between materials having different refractive indices, such as the interface between the pixel electrode and the interlayer dielectric, and the interface between the retention capacitance and the interlayer dielectric. Such reflected light provokes multiple interference, by which the intensity of the light transmitted through the interlayer dielectric is changed depending on the film thickness of the interlayer dielectric. Accordingly, the ununiform film thickness of the interlayer dielectric provokes fluctuation in spectral transmittance and color tone of the image displayed thereby degrading the display quality. Therefore, it is necessary to form the interlayer dielectric under control in a desired film thickness.
Besides, since the polish-away amount in the CMP process is mechanically controlled, in the case where a large polish-away amount is set to form the interlayer dielectric it is difficult to adjust the film thickness to the desired level because of increased mechanical fluctuation. Accordingly, the polish-away amount has to be set as small as possible when forming the interlayer dielectric.
On the other hand, reducing the polish-away amount in the CMP process makes it difficult to completely remove projections and recesses on the surface of the interlayer dielectric reflecting the shape of the retention capacitance, in other words projections widely formed in the retention capacitance region, and the global gap is formed along the outer periphery of the retention capacitance region. The alignment of the liquid crystal molecules is disturbed in the vicinity of the global step, and consequently the display becomes uneven.